Most industries face significant liquid/solid waste disposal problems. Such waste typically comprise a substantial solid phase containing an organic component that can be moved by or dispersed in a liquid substantially aqueous mobile phase. The aqueous mobile phase can be reused while the solids are continually separated. The solid phase can often contain a broad range of particle sizes and a large proportion of organic (e.g.) food related residues including carbohydrates, fats, proteins and other materials of biological origin. Of particular concern in the area of solid waste management is the production of strong or offensive smells or off-odors produced during operations of such waste handling systems.
One particularly sensitive area of solid waste management involves enclosed aqueous/solid waste handling systems having anaerobic sections. Such systems can include processing units such as waste pulpers or grinders (food disposals), pumps, lines, tanks, solids extractor components, etc. In such systems, waste is commonly obtained in the form of a slurry or dispersion of solid waste material in an aqueous liquid carrier or medium. Such waste is generated in that form or is converted to that form by equipment that grinds, pulps, shreds or otherwise reduces solids in the waste stream into a particle size that can be dispersed into a liquid carrier medium for transportation through the system. The slurry or dispersion of solid waste in the liquid medium is typically directed to a solids extractor or separator that, using a physical process, separates the waste into a solids portion containing a relatively smaller or reduced portion of the aqueous medium from a portion comprising the majority of the aqueous medium. The aqueous medium is then either reused, treated for other uses or discarded into municipal waste treatment systems. The solid waste with a minimal amount of water can then be directed to incinerator disposal, landfill disposal, or other appropriate disposal modes. In the anaerobic sections of the system, anaerobic microorganisms grow by utilizing soluble materials and waste solids as a source of energy and growth. Such activity can also result in odor generation.
Within the enclosed system, a collection of processing equipment is installed for the purpose of collecting the waste, adjusting the waste to the appropriate form in a pumpable system, directing the slurry or dispersion of aqueous waste to a solid extractor for removal of solids from the aqueous waste while the aqueous material is then maintained in a holding tank. The inherent nature of such enclosed systems results in a proportion of the system that is maintained under substantially anaerobic, substantially oxygen reduced, conditions. Under such conditions, in the presence of food waste including fatty, carbohydrate and proteinaceous soils, the growth of substantial proportions of anaerobic microorganisms can be promoted. The anaerobic microorganisms use the food waste as a source of energy and produce as a result of their microbial activity, off-odors resulting from nitrogen metabolism, carbon metabolism, sulfur metabolism or other microbial action. One particularly offensive odor results from the production of relatively small C.sub.2-6 carboxylic acids that have a characteristic "vomitus" anaerobic odor. The odors can be detected during careless operations and when small leaks arise from acid promoted corrosion.
The prior art shows three methods of controlling the production of off odors. The first method involves the careful operation of such systems such that the microorganism growth is prevented by careful operation including flushing the system with water with sufficient frequency to purge the system of substantial numbers of microorganisms. A second useful control mechanism involves the introduction of pleasant masking odors into the system to mask the off odors when released into the close by environment. A third useful control mechanism involves the introduction of competing microorganisms into the system to replace the odor generating microbes with a population that has reduced quantity of odor or odors of a reduced offensive nature.
Such anaerobic enclosed systems are particularly difficult to deal with in hospitality installations having a high degree of soil load containing a large proportion of food derived waste. Such systems are common in hospitality locations serving relatively large populations in relatively small locations such as hospitals, hotels and cruise ships. In these environments, the production of off odors is particularly problematic due to the closeness of large numbers of sensitive individuals to the source of the odor and the intensity of the generated odors.
A mobile waste treatment facility is shown in the prior art. Russell et al., U.S. Pat. Nos. 5,336,398 and 5,520,803 disclose an aerobic portable waste water treatment device open to the ambient atmosphere that is adapted to treatment of industrial waste water. One specific waste stream is generated by marine cargo container cleaning or wash out operations. In such operations, marine cargo containers are cleaned in port and the resulting waste water is treated and disposed. The Russell et al. treatment process uses an oxidizing agent in a first reactor tank. The resulting treated composition is neutralized to a pH between 7.5 and 9.4 in order to precipitate heavy metals from the material. The supernatant is pumped through a filter to yield a waste water that can be disposed or reused. The precipitate sludge is accumulated, thickened, dewatered and disposed in a landfill. The system in Russell et al. is largely aerobic, uses an oxidizing agent, contains minimal organic wastes and is not used in areas sensitive to odor production.
Accordingly, a substantial need remains to obtain an organic waste handling system that can be operated without the production of offensive odors.